Generally, among display devices, a liquid crystal display (LCD) device has been used in a variety of devices including a television, a laptop computer, a monitor for a desktop computer and a mobile telephone.
Since such a liquid crystal display device is not of a self-luminous type, it requires a light-emitting unit to irradiate a liquid crystal display panel in displaying an image.
The light-emitting unit of the liquid crystal display device is called a backlight unit because it is disposed on a rear face of a liquid crystal display panel. The backlight unit forms uniform surface light and supplies it to the panel.
A conventional backlight unit includes a light source, a light guide plate, a diffusion sheet, a prism, a protection sheet, etc. and may generally employ as the light source a fluorescent lamp such as a mercury cold cathode fluorescent lamp or a light-emitting diode.